Chaser



March 7, 1939. K. w. REED ET AL GHASER Filed June 18, 1936 5/ fi. Way/er"vii Patented Mar. 7, 1939 UNITED STATES PATENT OFFICE GHASERcorporation of Ohio Application June 18, 1936, Serial No. 85,872

3 Claims.

This invention relates to chasers or cutting dies for thread cuttingmachinery and has for its purpose the application to such dies aprinciple of tooth formation whereby appreciable saving in power may beaccomplished without sacrifice of accuracy or of cutting efiiciency. Thechasers shown in Figs. 1, 2 and 4 represent embodiments of our inventionin its general application, whereas the chasers of Figs. 3 and representexceptional embodiments which may under certain circumstances be used,optionally, in connection with the general formation.

This invention is susceptible of application in a variety of forms. Suchvariations of form are determined either by the character of the threadto be out, such as tapered or straight, the crosssectional shape of thethread, the nature of the material, such as steel, iron, brass, and soon, or by the size of the work, which is important as determining theshape and dimensions of parts of the chasers to be used. Our invention,therefore, can be applied to more than one style of chaser or chasertooth with variations dependent upon the shape of the entire chaser orby the purposes to which it is to be applied.

To the accomplishment of the foregoing and related ends, said invention,then, consists of the means hereinafter fully described and particularlypointed out in the claims.

The annexed drawing and the following description set forth in detailcertain structure embodying the invention, such disclosed meansconstituting, however, but one of various structural forms in which theprinciple of the invention may be used.

In said annexed drawing:

Fig. 1 is a perspective view of a chaser to which our invention isapplied having only a few teeth;

Fig. 2 is an end View of the chaser shown in Fig. 1;

Fig. 3 is a corresponding view of a chaser of the same type, but with areversed tooth formation as will be explained in the specification;

Fig. 4 is a perspective of the toothed end of a chaser with a largernumber of teeth and in which the principle is applied in another manner;

Fig. 5 is a perspective corresponding to Fig. 4 but in reverse, asexplained hereafter;

Fig. 6 is an enlarged diagrammatic showing of two tooth ends forexplaining the principle of the invention;

Fig. '7 is a diagrammatic perspective for use in the explanation of Fig.6; and

Fig. 8 is a front elevation of a die stock equipped with chasersaccording to the present invention.

The chasers of Figs. 1, 2 and 3 show the application of our invention toshort chasers having only a few teeth, and thus having a shank l or I ofapproximately square cross section. The working end of the chaser isbased upon standard construction in that the throat 2 and teeth 3, 4 and5 are disposed in the usual relationship, the embodiment shown being fora taper thread, and the entering edge 6 is undercut as at 7-1 to givethe usual top rake. However, the undercut portion or chip groove 9 isalso inclined from front to rear along the entering edge 6 and itsintersection with the teeth 3, 4 and 5 so as to make an angle with thetooth body at the entering end of each tooth. In the embodiment shownfor illustrative purposes herein, this angle a in Fig. 2 isapproximately 25. That is, taking the entering edge as a line from thepoint ill to the point 15, this line |0-l5 as best seen in Fig. 2, makesan angle of about, 25 with the side of the body I. This angle is shownas side rake and so referred to in this specification and claims.

Although our invention is not limited to any specific angle of siderake, angles on the order of from to 45 have been satisfactory. One

factor in determining the side rake angle to be employed is theconsideration that the rear teeth 5 must not be too short. For example,the land distance -35 must be sufficient to maintain necessary strengthof the tooth, having regard for the material to be cut, and otherpertinent factors.

It will be observed that the leading end of the tooth structure in Figs.1 and 2 is of a somewhat complex shape due to the curvature of theundercut portion, wherein top rake is superimposed upon side rake. Theentering points I 3, l4 and I5 of the teeth 3, 4 and 5 respectively thusoverhang to some extent, having the usual top rake which is thus bestillustrated by the dotted line 1, Fig. 2, and is also visible in Fig. 1.In our improved form the cutting is done principally by the leadingedges such as 44 of the tooth 4 and 45 of the tooth 5.

Before describing the chaser shown in Fig. 3, we will explain themodified application of the principle of our invention which isillustrated in Fig. 4. Here the chaser is one having many teeth andconsequently greater depth in the axial direction of the work than inthe chaser of Fig. 1. Obviously to put side rake on this .so onthroughout the chaser.

ployed will be best understood by reference to the shown, 6| and 62.

diagram of Figs. 6 and 7. Heretwo teeth are For simplicity these areillustrated as though formed entirely of plane surfaces and straightlines, all the curvature of lines and planes which characterizes theconstruction in an actual chaser being omitted. On this basis,

the front or entering face of the tooth 6|, in the prior art form, isconsidered as a triangular plane bounded by the actual lines 63 and 64and the imaginary line 65. The line 65 is drawn simply from the root ofone tooth to the root of the next, delimiting the tooth end surface fromthe shank,

' or more strictly, from the face of the chip groove.

In order to apply the principle of the invention it is necessary to havethe cutting edge 63 sharpened to acuteness, and this is done by removingthe portion of metal shown in Fig. 7, which for theoretical purposes maybe considered as a pyramid having the slant edges 63, 64 and 66 and base61,68. In Fig. 6 and Fig. 7 the lines 63 and 66 are shown solid becauseboth represent edges common to the finished tooth and to the removedpyramid. In Fig. 6 lines 64 and 65 are shown dotted because they are notpresent in the finished tooth, but they are shown solid in Fig. 7because if the endshape was made by removing single piece they would besolid. v

, Our invention may be applied as shown in Fig.

i 4 where the lines 53, 55, 56 and '5'! correspond respectively to thelines 63, 65, 66 and 6'! of Fig.6. Referring to Fig. 6 for a comparisonbetween Figs. 2 and 4, it will be observed that the angle a of Fig. 2,which we term the side rake angle, is

' definedin Fig. 4 for each tooth, and is the functional equivalent ofthe angle a of Fig. 6. (The angles aand a are not actually equal in the.drawing because Fig. 6 is adapted from a specimen other than Fig. 1.)If the same angle of side rake is applied to Fig. 4 as to Fig. 2it will'be applied by so shaping the tooth ends of Fig. 4

as to leave the angle 0 of Fig. 6, which is the complement of'a'... IfFig. 4 and Fig. 1 are to have equally acute teeth a must equal a, butour invention is capable of being embodied within a wide angular range.What has happened in Fig. 6, therefore, is that the face 63, 64, 65 hasbeen cut back by removing the pyramid, of Fig. 7 so that the right angleb ordinarily used in chaser teeth has been reduced by the amount of theangle a leaving the acute angle 0., In Figs. 6 and 7 the tooth root isindicated by the line 68, a portion of which forms one of the base lines68 of the removed pyramid. Of course in Fig. '7 the line 61 is showndotted simply because it is concealed behind the front and side faces.

all the relationships of Fig. 6 reversed. Such a modification of thechaser of Fig. 1 is shown in V .at' the rear than at the front, bringingthe point" 1A nearer than the point I to the side IA. That is, the siderake slopes outward from front to rear. As a consequence, the sharpenedslant edges of the variousteeth will be at the rear as 45A, MA and soon, being the trailing edges in' the direction of work feed. Applyingthis reverse 7 arrangement to Fig. 5, there is no side component.

to the top rake cut 59A, but each tooth is in clined' at its end in thesame manner as at 53, 56of Fig. 4, but in opposite sense. Thus the acuteedges such as 56A are the trailing edges, formed by the intersection ofthe tooth end surfaces with the'rear faces of the respective teeth.

It will be observed from the detailed figures that each tooth is givenits side rake by what may be considered an inclination of itsfrontalplane (that is, the plane of the entering face) about one of its sideslant edges, or in another wayof putting it, the entering faceis'relieved.

or approximately cylindrical surface-because the top rake is usuallyformed by a curved, not a plane, surface. Thus the edges which are shownas straight lines 63 and 66, Fig. 6, may actually be curved lines and ithas been attempted to so' indicate in Figs. 1 and 3, but the curvatureis' very slight and the showing is not noticeable in a perspective.details of possible intricacies ofshape for the purposes of thisdisclosure, since these may be varied without departure from theprinciples of the invention;

The application of our principle to actual work It is'not essential togo into the has shown a saving of about 30% in power re- 7 quired torotate the die stock with teeth so sharpened as to give a value of 15 tothe angle a, Fig. 2, and with diminishing power requirements as thesharpness of the leading edge increases.

This saving in power is believed to be due to the more effectiveshearing action upon the stock, accomplished by using an acute leadingedge of the tooth (see angle 0 Fig. 6) as compared With the formersquare edge (angle'b Fig.

6). Tests have not shown that the circumferential length of the teeth(distance 2535, Fig. 2) is an important factor. Therefore, as great orsubstantially as great a saving is accomplished by the form of Fig. 4 asby the form of Fig 1.

The chasers are for use in any conventional die stock such as Fig. 8,wherein four such chasers 8|, 82, 83 and 84 areillustrated. These ample,if 8|, 82 and 83 of Fig. 8 each represents a chaser of Fig. 1, 84 ofFig. 8 might either represent a chaser of Fig. 1 or a chaser of Fig. 3.

Similarly, if BI, 82 and 83 of Fig. 8 each represents a chaser of Fig.4, 84 of Fig. 8 might either represent a chaser of Fig. 4 or a chaser ofFig. 5.

From the foregoing it will be seen that we have discovered a principleand invented thread-cutting means and implements embodying thatprinciple whereby the cutting efficiency is increased. The invention maybe applied to existing threading equipment by reason of the fact that nochange in the general style and proportions of such equipment isrequired. 0n the other hand our invention is not limited to theembodiments shown.

Other modes of applying the principle of our invention may be employedinstead of the one explained, change being made as regards the structureherein disclosed, provided the means stated by any of the followingclaims or the equivalent of such stated means be employed.

We therefore particularly point out and distinctly claim as ourinvention:

1. A threading chaser comprising in combination a body, teeth on the endthereof all having the same top rake and a sharper angle at the enteringedge of each tooth than at the trailing edge, a chip groove adjacentsaid teeth with the side of the chip groove forming the entering ends ofthe teeth, said chip groove being shallow in front and deepening to therear.

2. A taper threading chaser having a plurality of teeth all of equal toprake and all of equal side rake, both rakes being formed by the chipgroove surface, said teeth being sharper along the front edges of theirentering ends than along the rear edges of the entering ends, and saidchip groove so inclining from front to rear as to make the rear teethshorter than the front teeth.

3. A threading chaser comprising in combination a body, teeth on the endthereof all having top rake in the same positive direction and a sharperangle at the entering edge of each tooth than at the trailing edge, achip groove adjacent said teeth with the side of the chip groove formingthe entering ends of the teeth, said chip groove being shallow in frontand deepening to the rear.

KENNETH W. REED. HARRY A. MAURER.

